Welcome to Bimmerfest -- The #1 Online Community for BMW related information! Please enjoy the discussion forums below and share your experiences with the 200,000 current, new and past BMW owners. The forums are broken out by car model and into other special interest sections such as BMW European Delivery and a special forum to voice your questions to the many BMW dealers on the site to assist our members!

Could anyone help shed some insight on the differences in transmission used in the 28i versus the 35i?

The 28i has an 8-speed transmission whereas the 35i uses an (older) 6-speed transmission. I thought there must be a reason why the 6-speeds are used on the more powerful car as it seemed inferior to the 8-speed, especially when all the X3's and X5's I see in a deal use the newer-looking 8-speed transmission.

What does that do performance-wise?
Maintenance? (probably more expensive on the 8-speed... how much?)
Any opinions at all?

BMW tends to pair an engine with a particular transmission. The N20 engine used in the 28i models was designed with the 8-speed because it is a new engine just recently released in January 2011. On the other hand, the 35i model uses the older N55 engine which dates back to late 2009 with the E90 architecture in the 335i. While I realise that the N55 is now paired with the 8AT in most other BMWs, I'm sure there's probably some packaging limitations in the X1 due to its smaller size and shared architecture with the E91.

The 8-speed is a more advanced transmission. More efficient, shifts faster, and more responsive. Maintenance-wise, both are costly and complex to repair. Both are ZF-built. I'd just get the 28i with the 8-speed autobox.

Just a personal observation: we went from a e46 6speed to the x1 28 today. It feels like its always shifting with the extra gears. I'm sure ill get used to it soon but its just kinda strange.

I test drove the 8-speed extensively twice and I agree. Always shifting. Drove me nuts. May drive me away from BMW, especially since when you manually select a gear in sport mode, the darn thing still tries to out-think you by downshifting anyway if you give it too much accelerator.

BMW tends to pair an engine with a particular transmission. The N20 engine used in the 28i models was designed with the 8-speed because it is a new engine just recently released in January 2011. On the other hand, the 35i model uses the older N55 engine which dates back to late 2009 with the E90 architecture in the 335i. While I realise that the N55 is now paired with the 8AT in most other BMWs, I'm sure there's probably some packaging limitations in the X1 due to its smaller size and shared architecture with the E91.

The 8-speed is a more advanced transmission. More efficient, shifts faster, and more responsive. Maintenance-wise, both are costly and complex to repair. Both are ZF-built. I'd just get the 28i with the 8-speed autobox.

Thanks for the clarification!

Anyone's got experience/knowledge of failure rates for the two transmissions?
I felt that it's borderline overdoing it when the parking break is electronic.

I test drove the 8-speed extensively twice and I agree. Always shifting. Drove me nuts. May drive me away from BMW, especially since when you manually select a gear in sport mode, the darn thing still tries to out-think you by downshifting anyway if you give it too much accelerator.

Did the constant shifting happen during mainly driving on local roads or highway?
I'm a fairly mellow driver (when it comes to driving BMW's anyway) so didn't notice too much shifting.

Steady driving on freeway obviously it's not shifting at all unless you are constantly accelerating or decelerating. It is noticeable how in city driving it prefers a really low gear, so it seems like it shifts a lot to get there. This is minimized when in sport mode (DS), because the shifting programming is more aggressive (i.e. higher gear), which I am pretty sure is the only thing that sets "sport mode" apart from normal drive mode.

By the way, I pulled out in traffic after getting gas yesterday and had to gun it, and I let out another "WOW" as I punched it. This engine is awesome when it spools up. There is a ton of lag when you give the car gas unless you really step down on the accelerator. I wonder how much of the 6.2 sec 0-60 time is just engine and transmission responsiveness. I wonder if remapping it would get closer to the 5.6 sec zero-60 the 328 N20 does. When the turbo spools up it really kicks you in the seat of the pants!

By the way, I pulled out in traffic after getting gas yesterday and had to gun it, and I let out another "WOW" as I punched it. This engine is awesome when it spools up. There is a ton of lag when you give the car gas unless you really step down on the accelerator. I wonder how much of the 6.2 sec 0-60 time is just engine and transmission responsiveness. I wonder if remapping it would get closer to the 5.6 sec zero-60 the 328 N20 does. When the turbo spools up it really kicks you in the seat of the pants!

Most if not all automatic transmissions are programmed to minimise fuel consumption and emissions, hence the tendency for the gearbox to quickly shift into the higher gears (5-6-7-8) even at moderate speeds. Furthermore, generally transmissions can be reluctant to downshift unless you stab the throttle or hit the kickdown, and with the torque converter locked up immedately after starting off, there's far less of the "slush" that used to allow the revs to rise before the gearbox actually changed down a gear or two.

However, once you hit the kickdown, the vehicle does maximum acceleration regardless of shifter position so throttle calibration isn't so much an issue there.

Full disclosure: I have yet to test drive an X1 or X3 with the 8-speed gearbox.

If you think urban acceleration is exciting, wait till you get on a mountain road and really do some driving. The programming can be hit-or-miss at times in urban driving but when it detects very aggressive driving, it'll hold gears to redline and downshift early under braking so that you're in the optimal gear when exiting the corner. Since the transmission is adaptive, it won't go into this mode after a few throttle kickdowns, rather it takes into account the duration and frequency of throttle inputs, lateral acceleration, and braking inputs over a brief period of time and adjusts accordingly. It renders (in my opinion) the Steptronic function pointless.

Here in Canada we have had the X1 for a couple years now. I started test driving the 2012 X128 last year with the 8-speed auto. We really wanted a manual transmission and thought we would have to put up with a boring automatic transmission. One block with the X128 and I knew we could live with that transmission. It is energetic and exciting.

We were at the dealer two weeks ago (after our 5th test drive in the X128) custom ordering our new baby. I remembered seeing an X1 very similar to the one we were spec'ing already on the lot, so I asked about it. It was the X135. We didn't want the larger engine and 6-speed tranny, so we continued with the order.

Our salesman (saleswoman Eve actually) read us like a book. She told us to take the X135 for a little spin in the parking lot. Since it hadn't gone through PDI (Post Delivery Inspection, I think) it could not be driven on the road. So we tooled up and down the parking lot a bit. Reving up to 4000 RPM in a parking lot with 300 hp under the bonnet was incredible. With their one year anniversary sale (BMW Langley, BC) our custom ordered X128 was the same price as the X135 already sitting on the lot. So we bought the X135 and have put on 900 km of the 2000 km break-in period (under 4500 RPM for 2000 kms). It was the first X135 sold at that dealer.

If the X135 had that 8-speed transmission, I think it would fire through the gears too quickly. As it stands with the 6-speed transmission, you get a low first gear and well balanced taller gears. It still feels like it shifts a lot to give you the power you need, but nearly as much as the X128. It actually feels a little bit like the 1991 Alfa Romeo 164S we used to have, beautiful power from low revs all the way up to ... well 4500 RPM.

Also, the X128 had the electronic joystick shifter. It was fine, but I don't think my Mom could borrow the car because it'd be too complicated for her. I know my Mom would have been able to drive somewhere, and stop, apply the e-brake, and not know how to put it in park. She could turn off the engine but not be able to take the key out because it's not in park. She would then call me to say what a stupid vehicle I have and then make me come down and show her AGAIN how to park it.

The X135 has a more conventional mechanical shifter. Press the lever and move the shifter into D, done. Compatible with my mother's 65 year old brain.

So to sum up this boring tale:
1) The X128 has a fantastic engine and energetic 8-speed transmission,
2) The X135 has a massively powerful engine and a well suited 6-speed transmission.
3) Test drive them both!

Anyone have pics of the rear exhaust on a 2013 X1 35i and X1 28i? (specifically from a lower angle)
So far, I've noticed the exhaust tip and muffler hang a little lower on the 28i compared to the 35i.
My closest dealer is about 800KM away, so I've been trying to find some good pics on the net to really compare the 2.

So to sum up this boring tale:
1) The X128 has a fantastic engine and energetic 8-speed transmission,
2) The X135 has a massively powerful engine and a well suited 6-speed transmission.
3) Test drive them both!

Cheers.

Thanks for the insights. I did test drive both briefly. Will have to test drive them again as I was driving rather politely on the 35i. Probably won't be as lucky as you are to find an already built car that fits your configuration with a discount (The X1 is new in the USA and I don't previously own any BMW's).

Anyone have pics of the rear exhaust on a 2013 X1 35i and X1 28i? (specifically from a lower angle)
So far, I've noticed the exhaust tip and muffler hang a little lower on the 28i compared to the 35i.
My closest dealer is about 800KM away, so I've been trying to find some good pics on the net to really compare the 2.

Anyone's got experience/knowledge of failure rates for the two transmissions?
I felt that it's borderline overdoing it when the parking break is electronic.

I am pretty sure the parking brake is mechanical on the X1. The transmission selector is electronic though. If a car with the 8 spd gets a flat battery or the has a computer problem, it will not be possible to shift it out of park. A BMW tech will need to go under the car to release the transmission. This won't be required with the 6 spd.

I am pretty sure the parking brake is mechanical on the X1. The transmission selector is electronic though. If a car with the 8 spd gets a flat battery or the has a computer problem, it will not be possible to shift it out of park. A BMW tech will need to go under the car to release the transmission. This won't be required with the 6 spd.